1. Field of the Invention
This invention concerns improvements in and relating to implements, more particularly to the means of connection and mounting of implements for working the soil to tractive vehicles fitted with the usual three arm lift. A useful application of this invention lies in the field of agricultural implements.
2. Description of the Prior Art
For example, in regard to agricultural ploughs the appearance of tractors capable of exerting ever greater tractive powers has enabled increasing rates of ploughing of land area. The necessary increases in the size of ploughs has, however, inherently tended to place a limitation on the use of fully mounted implements with the usual three arm lift. This is generally because a practical limit is reached beyond which the handleability and manoeuvreability qualities of the tractor and plough combination become poor, to such an extent that the potential advantages of such large and powerful tractor-plough combinations are not realised in practice.
Such problems are enhanced in areas where contour ploughing is necessary and where accordingly swivel mounted ploughs are employed. The major problem which arises with increasing size of ploughs is that the plough cannot be lifted clear of the ground since the leverage exerted by its mass becomes so great that the front wheels of the tractor are lifted or the capacity of the three arm lift is unequal to the task. In regard to soil working elements such as plough shares, the share which exerts its action below the surface of the ground must of necessity be mounted on a frame located above the surface of the ground and this results in large torsional forces tending to twist the framework on which the shares are mounted. For reasons such as this the usual practice has been to mount the shares on a beam type of framework aligned fairly close to the direction of tractive effort exerted on the implement so that substantially the full length of the beam is available for counteracting the torsional forces referred to. The beams are angled somewhat in order to provide a transverse width of coverage. In order to fully utilise the large power of tractive powers available in current tractive vehicles a large number of shares must be mounted thus furnishing an increased width ploughed in each pass but introducing the disadvantage that the beams become very long of necessity and as a result can no longer be fully mounted since the lever arm exerted by the mass of the shares on the tractive vehicle becomes very high. Accordingly so called semi-mounted ploughs have been employed, these riding permanently on wheels mounted on the plough which are also given a facility for steering. The manoeuvreability and handleability qualities of such semi-mounted ploughs is, however, poor and particularly in areas requiring contour ploughing and frequent turn-abouts they exhibit severe problems in their use.
The Pat. No. 3039541 granted to E. A. Harden et al. deals with a class of implement which is exemplary of the above described prior art. It shows a powerful tractor pulling a large plough. The plough is, however, semi-mounted, that is it runs on its own wheels, with the resulting disadvantage that the downwards forces resulting both from its weight and the action of the soil on it during ploughing are carried by its own wheels and are not transferred to the tractor. This tends to result in wheel slip of the driving wheels of the tractor as compared with the fully mounted plough which transfers these downward forces to the tractor giving the driving wheels greater traction. This wheel slip places a limitation on the size of a semi-mounted plough that can be pulled and prevents utilization of the full power available from modern tractors. Also, the plough is not swivel mounted which makes it very difficult to plough curves in contour ploughing. The tractor-plough combination is shown as capable of lifting the plough, but the length and weight of plough which can be lifted as shown is limited by the problems mentioned above. This again tends to cause under utilization of the full power available from the modern tractors since a large enough plough of this type to match the tractor power cannot be lifted.